Anti-blinding wiper assembly for vibratory separator

ABSTRACT

A vibratory screen separator including a horizontal separator screen, is provided with a wiper assembly disposed above the horizontal separator screen and operative to dislodge portions of substance which may coat the upper surface of the vibratory screen. The wiper assembly generally comprises a flexible cover means to which is attached a plurality of wiper members, with the wiper members being disposed between the upper surface of the separator screen and the cover means so as to space the cover means from the screen thereby preventing splashing of the substance to be separated when it is introduced between the cover means and the separator screen. Wiper blade members are caused to move across the separator screen in such manner as to dislodge portions of substances which may build up and obstruct holes in the upper surface of the separator screen.

nited States Patent 1191 Gray Feb. 4, 1975 ANTI-BLINDING'WIPER ASSEMBLY FOR VIBRATORY SEPARATOR Primary Examiner-Tim R. Miles Assistant Examiner-Ralph J. Hill [76] Inventor g i' g g i g gfig g ifjggg Attorney, Agent, or FirmThomas M. Marshall PP A vibratory screen separator including a horizontal separator screen, is provided with a wiper assembly 52 us. c1 209/323,-209/389, 209/390 disposed abov? the horiomal Separator Screen and 51 Int. Cl 3071) 1/52 Operaflve to dlslodge P n of ubstance whlch may [58] Field of Search 209/385, 386, 389, 390, 9 the PP Surface of the "b f The 209/320, 323 332, 324, 358, 351,384, 325 wiper assembly generally comprises a flex ble cover 7 means to which is attached a plurality of wiper mem- [56] References Cited bers, with the wiper members being disposed between the upper surface of the separator screen and the UNITED STATES PATENTS I cover means 'so as to space the cover means from the 2 fii z i screen thereby'preventing splashing of the substance 1 i a to be separated when it is introduced between the if fii f i cover means and the separatorscreen. Wiper blade members are caused to move across the separator FOREIGNPATENTS 0R APPLICATIONS screen in such manner as to dislodge portions of subl,23l,l52 9/1960 France 1.1 209/386 stances which may build up and obstruct holes in the 623,742 /1949 Great Britain.... 209332 upper surface of the separator screen. 1,188,412 9/1959 France 209 390 1,807,711 5/1970 Germany 209/389 Clams, Drawmg Flgures I H 4.Am!- l 64 '56 6/ 69 24? W M l 32.

40 A? 1 as l l 44 Z 4e 66 6'4 42 I1 I f0 I ll FIELD OF INVENTION The present invention relates to vibratory separators, and more particular to vibratory separators having antiblinding devices. The invention is more particularly, but not exclusively, directed to vibratory separators of the class in which a gyratory and oscillatory tilting motion is imparted to the screen and the casing to which it is attached by means of a motor rigidly mounted on the casing and provided with eccentric weights on its shaft. Blinding is the name attributed in the art to the phenomenon according to which part of the material which is being screened lodges in the apertures of the screen, blocking or blinding part of the area of the screen and thus reducing the speed and efficiency of separation. An example of a vibratory separator to which the present invention is directed is described in US. Letters Pat. No. 3,508,649 entitled Anti-Blinding Device For Vibratory Separator which issued on Apr.

28, 1970 to Bernard Kahane and Ronald H. Stewart, and is assigned to the assignee of the present invention, Separator Engineering Ltd., Montreal, Quebec, Can.

DESCRIPTION OF THE PRIOR ART As noted in U.S. Letters Pat. No. 3,508,649, various solutions have been proposed for dealing with the problem of blinding. Ingeneral, the solutions involve the provision of locating elements, such as balls in a subsidiary or supporting screen disposed below the main separator screen so as to be vibrated with the separator screen. In this location, the elements move at random in the gap between the support and separator screen and strike the underside of the separator so as to dislodge trapped material either by direct impact or by the secondary vibration which the impacts induce in the screen materiaLWhen the elements are in the form of balls, the balls are effective to remove near-sized particles that lodge in the screen openings by impact, knocking them out. In those systems wherein the elements are in the form of cylinderal rings, the rings strike the underside of the separator screen in amanner to provide a glancing blow, thus shearing off fibers or other materials that tend to stick through the screen openings. The type of blinding that these devices is effective in eliminating is that caused by materials that coat the upper side of the wires of the working or separator screen, building up to eventually block off the openings. Neither the balls nor the rings can get at these build-ups to dislodge them. This type of blinding is most often caused by materials suchas fats, pitch,

etc.

SUMMARY OF THE INVENTION means for preventing blinding on the upper portion of' tribute its action as it cleans the entire upper screening surface of the separator screen.

It is another object of the invention to provide a wiper assembly disposed on the upper or top side of the separator screen which is of light weight so as to produce a minimum amount of abrasive action or mechanical working of the screen cloth, so as not to shorten the working life of the separator screen cloth.

It is another object of the invention to provide a wiper assembly for the upper surface of a generally horizontal separator screen of a vibratory separator of the type wherein oscillatory-gyratory motion of the vibratory separator induces materials fed to it to follow a certain path from a central feed point to the discharge spout. This motion can be adjusted to effect the shape and length of this path, and this same propulsive force can cause a properly designed and constructed wiper means to move along the screen surface, thus fulfilling the requirement for a wiper assembly that covers the entire upper surface of the separator screen without any additional external motive power.

It is another object of the invention to provide an anti-blinding wiper assembly which is designed so as to move along the upper surface of the separator in a free manner, and not bounce up and down due to the vertical forces imparted to it by the vertical motion of the machine. As is readily apparent, bouncing reduces the effectiveness of the scraping action, in that the wiper assembly cant scrape while it is bouncing out of contact with the screening surface and the constant hammering of the screening surface results in the rapid deterioration of the screen surface.

In accordance with one aspect of the present invention there is provided a vibratory separator having a horizontal separator screen, and provided with a wiper assembly in the form of an annular cover means made the separator screen in the form of a'wiper assembly which is so constructed that it requires no power to disof flexible material of slightly smaller diameter than the annular casing of the vibratory separator, which cover means is disposed above and freely moveable relative to said separator screen. The cover means includes a central opening for enabling the substance to be separated to be passed to the region intermediate the cover means'and the separator'screen. In addition, the wiper assembly includes a plurality of radially-extending, elongated wipermembers secured to the underside of theannular cover means thereby maintaining the cover means at a spaced distance from the upper screen surface to enable the substance to be separated to move along the upper surface of the screen..

In an alternate embodiment, the wiper members take the form of arcuate members which are secured to the cover means, preferably pivotally secured, so as to permit adjustment of the motion imparted to particules with which the wiper members come into contact while moving relative "to the upper surface of the separator screen. I

As the wiper assembly of the subject invention moves over the upper surface of the separator screen, it lightly scrapes the upper surface of the separator screen, and

as such is effective in removing films before they have a chance to anchor themselves to the screen surface and build up a blinding coating.

The wiper assembly of the subject invention is so constructed so as to require no power to distribute its action while it cleans the entire upper surface of the separator screen. Furthermore, it is light enough so as to producelittle abrasive action or mechanical working of the screen cloth of the separator screen so that it does not shorten the working life ofthe cloth to any significant extent.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, and to show how it may be carried into effect, reference will now be made to a preferred embodiment and an alternate embodiment, described and illustrated with reference to the accompanying drawings in which:

FIG. 1 is a vertical cross-section through a vibratory separator in accordance with a preferred embodiment of the invention;

FIG. 2 is a top view of the preferred embodiment of the wiper assembly of the subject invention;

FIG. 3 is a bottom view of the preferred embodiment of the wiper assembly of the subject invention;

FIG. 4 is a sectional view of the wiper assembly taken along line 44 in FIG.- 2;

FIG. 5 is a partial vertical cross-section through a vibratory separator including an alternate embodiment of the wiper assembly of the subject invention;

FIG. 6 is a top view of the alternate embodiment wiper assembly illustrated in FIG. 5; and

FIG. 7 is a bottom view of the alternate embodiment of the wiper assembly of the subject invention.

FIG. 8 is a top plan view of still another alternate embodiment of the cover means showing the partial slits along radial lines;

FIG. 9 is a cross-sectional view taken along of FIG. 8 and showing the cover means partially engaging the separator screen; and

FIG. 10 is a top plan view of still a further embodiment of the wiper comprising brushes.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1, the vibratory separator includes a stationary cylindrical base 10, and a separator frame 12 which is mounted on the base 10 by means of plurality of springs 14 thereby forming a free floating connection between the cylindrical base 10 and the separator frame 12. Each spring 14 extends between an upper peripheral flange 16 of base 10 and the lower surface 18 of the frame 12. The lower surface 18 is secured so as to be rigged with a motor enclosure 20. Electric motor 22 is mounted to the enclosure by means of mounting rings '30 which encircle the motor 22. The latter is connected by a lead wire 24 to a switch 26 mounted externally of the base 10.

The lower mounting ring is seated in sloping end surfaces of'lower brackets 28 wich project inwardly from the enclosure wall, and the upper rings 30 are clamped by clamp elements 32 to upper brackets29.

Extending from the motor shaft 23 at the upper and lower ends thereof are mounting arms 34, 35 to which are attached eccentric weights 36, 38 respectively. The eccentric weights 36, 38 may be adjusted in lead and magnitude on the mounting arms 34, 35, and the assemblies of the arms and the weights are rotable about the motor axis 23 for adjustment.

Webs 42 interconnect the bottom 18 with the motor enclosure 20, to impart additional rigidity to the structure. It is apparent that due to the resilient mounting of the motor enclosure and frame 12, which are themselves rigid one with the other, the eccentric weights 36 and 38 cause a gyratory and oscillatory tilting motion lines 9 -9,

of the whole of the frame 12 and anything supported by the frame. I v

The frame 12 includes a lower cylinderal wall 44 having a lower peripheral flange 46 and an upper peripheral flange 48. The lower peripheral flange 46 and the rim of the bottom 18 are connected by a clamping ring 50.

Resting upon the lower cylindrical wall 44 is an upper cylindrical wall 5-4 having a lower rim 56. The rims '48 and 56 are of equal radial extension and are bent towards each other so as to facilitate their interconnection and clamping by a second clamping ring 58.

The upper cylindrical wall 54 has a peripheral outlet 60 surrounding by a downwardly directed spout 62, the purpose of which will become evident. The lower cylindrical wall 44 also has an outlet 64, which may be arranged as shown diametrically opposed to the outlet 60, and to which is attached a spout 66.

A deflector plate 68 is located within the wall 44 and is mounted thereto at is periphery by a suitable means, such as welding. The deflector plate 68 is bent about a diameter extending at right angles to a line interconnecting the center lines of the outlets 60 and 64, so as to have a horizontal half 70 and a downward sloping half 72 which leads to a point on the cylinder wall 44 below the outlet 64 in order to direct material falling from the deflector plate 68 to the outlet 64.

A separator screen 74 and a support screen 76 are mounted as at 78 by their peripheral rims at the junction of the frame walls 44 and 54. The mounting 78 for the separator and support screens is designed to provide a rigid spacing for the screens at the periphery and at the same time a convenient mounting arrangement for the screens within the frame 12.

The apertures of the support screen 76 should be at least as large and preferably considerably larger than the apertures of the separator screen 74, in order to allow material which has passed through the separator screen 74 to reach the deflector plate 68 without hinderance.

The parallel spacing between the screens 74, 76 is maintained at the center by means of a spacer ring 80. The screens have central apertures and the rim portion joining the apertures are embedded in epoxy resin retaining elements 82, the inner surfaces of which are separated by the spacing ring 80. A tie bolt 84 ispassed through a center aperture in the deflector plate 68, and its head is welded against the lower surface of deflector plate 68, and it passes through the central apertures in the screens. A metal plate including a gasket 92 of elastomeric material is disposed above the upper retaining element 82, and the assembly is held in place by adjusting nut 96 and lock nut 98.

Located between the support screen 76 and the separator screen 74, and resting on the support screen 76 are a plurality of anti-blinding rings 100. These rings are of cylindrical construction having-walls of substantial thickness, although the thickness is small compared with the diameter of the rings, so that passage of finer fraction of screen materials is unimpeded by the rings. It is preferred to employ sufficient rings to fill nearly or substantially all of the horizontal area of the support screen 76, which in the embodiment of FIG. 1 is equal in area to the separator screen 74. This arrangement ensures that the rings 100 move together with a circular motion and cover the entire area of the lower surface of the separator screen 76 as rapidly as possible.

Mounted on top of the upper surface of the separator screen 74 is the wiper assembly 110 of the present invention. The wiper assembly is freely mounted on the separator screen 100 so as to move along the separator screen's upper surface in response to the oscillatorygyratory motion of the separator.

Referring to FIGS. 1, 2, 3, and 4, a preferred embodiment of the wiper assembly 110 comprises a cover means 112 made of a flexible material such as rubber, and of a diameter less than the internal diameter of the upper cylindrical wall 54, as designated at 114. Secured to the flexible cover means are a plurality of wiper members 116, each of which comprises an elongated strip of a medium soft material, such as rubber, which is mounted within a U-shaped channel member 118 (preferably made ofa plastic material), with the rubber member 116 and the U-shaped plastic member 118 being bolted to-the cover means 112 by bolts 120. As illustrated in FIG. 3, the wiper members 116 extend vertically from the lower surface of the cover means 112 and are arranged in a spoke-like fashion. Referring to FIG. 4, in order to provide additional support for the flexible cover means 116, an annular disc 122 of approximately /8 inch thick rigid plastic is provided intermediate the upper portion of the U-shaped channel members and the flexible cover means, with the disc 122 being of smaller diameter than the cover means. The center of the disc 122 and the center of the cover means 112 include an aperture 124, and a collar 126 is bolted as at 128 to the cover means assembly. Also bolted to the collar is a smaller disc 130, preferably made of plastic having a central opening 132 of a diameter approximately A inch larger than the diameter of the feed pipe 140. The difference is size between the feed pipe 140 and the central opening 132 is indicated as at 142. The feed pipe, as -it is readily apparent, provides the substance to be separated to the vibratory separator. The disc 134 is high enough such that the end of the feed pipe 140 extends below the disc 134, and consequently the feed pipe acts a guide for the wiper assembly 110.

The wiper members 116 function to maintain the cover means 112 in spaced relationship above the upper surface of the support screen 74. As substance or'material to be separatedis fed from the feed pipe 140, it flows outwardly from the center of the wiper means adjacent the collar 126 to the space between the cover means 112 and the upper surface ofthe separator screen 74. As such, the cover means functions as an efficient anti-splash guard thereby inhibiting material from splashing out ofthe separator, and in addition aiding in the operation of the vibratory separator. More particularly, the surface tension created by passing liquid material to be separated over the screen cloth surface of the separator screen 74 and under the flexible cover means 112 could give rise to an increased capacity through the screen cloth separator surface, due to the induced shear action.

In the operation of the vibratory separator, the eccentric weights on the motor 22 impart a vibration to the unit consisting of the screens, the motor enclosure 20. the frame 12, and the wiper assembly 110, which has gyratory and oscillatory tilting components. The materials to be separated may be either a liquid/solid separation or a solid/solid separation, and are provided to the separator through the feed pipe 140. The material or substances to be separated passes from the feed pipe to the regiondefined between the cover means and the upper surface of the separator screen 74, and the vibratory and gyratory motions of .the vibratory separator cause the substances on the upper screen 74 to be given a series of radially outward and spiral impulses which move the material remaining on the separator screen toward and around the upper cylindrical wall 54 until it reaches the outlet 60. Similarly, materials which pass through the separator screen 74, the rings 100, and the support screen 76 fall onto the deflecting plate 68 where it moves around to the outlet 64. The vibratory and oscillatory movements of the separator causethe wiper assembly torotate about the central axis of the separator, with the disc 13 cooperating with the feed pipe to aid in guiding the wiper assembly. As the elongated wiper members 116 move around the separator screen, they lightly scrap the upper surface thereof, and accordingly are effective to remove material coatings or films before they have a chance to anchor themselves to the screen and build up a blinding coating on the separator screen. The wiper assembly 110 should be made of suitable materials, such as rubber and plastic, so as to require no power to distribute its action as it cleans the entire screening surface. In addition, the weight of the wiper assembly 110 should be light enough so as to produce little abrasive action or mechanical working of the screen cloth of the separator screen 74 so as to not shorten the working life of the screen.

FIGS. 5, 6, and 7 illustrate an alternate embodiment of the wiper assembly 110. In lieu of the elongated rubber members which extent radially from the cover means 112, the embodimentof FIGS. 5 through 7 provides an arrangement wherein the wiper member comprises a plurality of arcuate members 150, each secured to the cover means as 152, with the connection preferably being a pivoted connection so as to enable the arcuate member to be rotated about the fastener 152 to any desired angle. As illustrated in FIGS. 5 and 7 each arcuate wiper member 150 comprises one-half of a cylinder, with the flat edges-153, 154 of the halfcylinder being-parallel with the upper surface of the separator screen so as to obtain maximum contact area between the arcuate member and the separator screen.

It will be apparent that the wiper assembly of the subject invention may be employed with other types of vibratory separators or classifiers. Although several embodiments of the subject invention have been described inv detail, it is also readily apparent that other modifications and changes may be made without departing from spirit of the invention. For example, the medium soft rubber strips 116 may be replaced by bristle brushes as shown in FIG. 10, especially in those applications where the material to be separated consists of two solids. Also, in order to further inhibit splashing of a substance (e.g., when the substance consists of a liquid and a solid), the flexible cover means 112 of the wiper assembly illustrated inFIG'S. 1-4 may be radially slit as shown in FIGS. 8 and 9 on opposite sides of each wiper member from the outer diameter of the cover means to approximately the outer diameter of the intermediate disc 122. By this arrangement, the outer portions of the alternate cover means 162 would bend downwardly, as shown in the FIGS. 8 and 9, onto the upper surface of the screen, to serve as a splash barrier.

What is claimed is:

l. A wiper assembly for a vibratory separator including a generally horizontal separator screen mounted in an annular casing, said wiper assembly comprising:

an annular cover means of small diameter than said annular casing, for inhibiting splashing of material on said separator screen, said cover means being disposed above the separatorscreen and movable relative thereto, said cover means including an opening for enabling the substance to be separated to be passed to the region intermediate the cover means and the separator screen;

a feed pipe means for introducing said substance to be segregated to said opening in said cover means, said feed pipe means extending to an elevation which is lower than the elevation of the top of said opening whereby the lower portion of said feed pipe limits the excursion of said wiper assembly within an area which is approximately concentric with said annular casing; and

a plurality of wiper members secured to the underside of said annular cover means,'said wiper membersbeing operative to space the cover means from the screen to enable said substance to move along the upper surface of the screen, andsaid wiper members being operative, during operation of the separator, to move with the cover means relative to the screen in such manner as to dislodge portions of the substance which may coat the upper surface of the screen.

2. A wiper assembly as in claim 1 wherein the cover means is flexible.

3. A wiper assembly as in claim 1 wherein an opening is provided in the center of the annular cover means, which opening is slightly larger than a feed pipe for providing the substance to be separated to the vibratory separator.

4. A wiper assembly as in claim 1 wherein each wiper member is generally elongated and extends radially from the center of the cover means.

5. A wiper assembly as in claim 4 wherein each wiper member comprises an elongated, flexible member mounted in a U-shaped channel which, in turn, is secured to the underside of the annular cover means.

6. A wiper assembly as in claim 1 wherein each wiper member is arcuate inconfiguration and is pivotally secured intermediate its edge surfaces to the annular cover means.

7. A wiper assembly as in claim 6'wherein each wiper member is made of a flexible rubber material.

8. A wiper assembly as in claim 1 wherein the annular cover means comprises an annular flexible member of smaller diameter than said annular casing, and an annular reinforcing member of lesser diameter than said flexible member, which reinforcing member is secured to the lower portion of said flexible member.

9. A vibratory separator having an annular casing comprising:

a horizontal separator screen;

a support screen parallel to and below said separator screen and have apertures greater than that of said separator screen;

a plurality of anti-blinding rings having substantially flat upper and lower end surfaces disposed between said screen so as to be supported by said support screen;

a wiper assembly means mounted on the upper surface of and and freely movable relative to, said separator screen and said wiper assembly comprising an annular cover means of smaller diameter than said annular casing, said cover means including an opening for allowing the substance to be separated to be passed to the region intermediate the cover means and the separator screen, said wiper assembly means further including a plurality of wipers secured to the under side of said annular cover means, said wipers being operative to space the cover means from the separator screen to enable such substance to move along the upper surface of the separator screen, and said wipers being operative during operation of the separator to move with the cover means relative to the separator screen in such manner as -to dislodge portions of the substance which may clog the upper surface of said separator screen, and a feed pipe means for introducing said substance to be separated to said opening in said cover means, said feed pipe means extending to an elevation which is lower than the elevation of the top of said opening in said wiper assembly whereby the lower portion of said feed pipe limits the excursion of said wiper assembly within an area which is approximately concentric with said annular casing.

10. A vibratory separator as in claim 9 wherein the cover means is made of flexible material.

11. A vibratory separator as in claim 10 wherein the flexible cover means member is reinforced by a ring member of smaller diameter than said flexible cover means member.

12. A vibratory separator as in claim 9 wherein said cover means includes a central opening, with the size of the central opening being slightly greater than the size of the feed pipe for the substance to be separated.

13. A vibratory separator as in claim 9 wherein each wiper comprises an elongated member extending radially from the center of the annular cover means.

14. A vibratory separator as in claim 13 wherein each wiper comprises an elongated U-shaped channel member into which is fixedly mounted an elongated rubber member which engages the upper surface ofthe separator screen.

15. A vibratory separator as in claim 9 wherein each wiper comprises an arcuate member which is pivotally secured to the cover means at a point intermediate its edge surfaces.

16. A vibratory separator as in claim 15 wherein each arcuate member is made of a flexible material.

17. A wiper assembly for a vibratory separator including a generally horizontal separator screen mounted in an annular casing, said wiper assembly comprising:

an annular, flexible cover means of smaller diameter than said annular casing, said cover means being disposed above the separator screen and freely movable relative thereto, said cover means including a central opening for receiving a feed pipe to enable substance to be separated to be passed to the region intermediate the cover means and the separator screen; said feed pipe means extending to an elevation which is lower than than the elevation of the top of said opening in said cover means whereby the lower portion of said feed pipe limits the excursion of said wiper assembly within an area which is approximately concentric with said annular casing; and

a plurality of wipers secured to the underside of said annular cover means, said wipers being operative to sapce the cover means from the screen to enable said substances to move along the upper surface of the screen, said wipers being operative, during operation of the separator, to move with the cover means relative to the screen in such manner as to dislodge portions of the substance which may coat the upper surface of the separator screen.

18. A wiper assembly as in claim 17 wherein each wiper comprises an elongated member extending along a radius of said annular cover means, each wiper comprising an elongated U-shaped channel secured to the cover means, and having mounted therein an elongated, flexible wiper member which is adapted to contact the upper surface of the separator screen.

19. A wiper assembly as in claim 17 wherein each wiper comprises an arcuate member pivotally mounted to the annular cover means.

20. A wiper assembly as in claim 17 wherein the cover meansis partially slit along radial lines in such manner that the outer peripheral portions of the cover means engage the separator screen.

21. A wiper assembly as in claim 17 wherein each wiper comprises a brush.

* k i l 

1. A wiper assembly for a vibratory separator including a generally horizontal separator screen mounted in an annular casing, said wiper assembly comprising: an annular cover means of small diameter than said annular casing, for inhibiting splashing of material on said separator screen, said cover means being disposed above the separator screen and movable relative thereto, said cover means including an opening for enabling the substance to be separated to be passed to the region intermediate the cover means and the separator screen; a feed pipe means for introducing said substance to be segregated to said opening in said cover means, said feed pipe means extending to an elevation which is lower than the elevation of the top of said opening whereby the lower portion of said feed pipe limits the excursion of said wiper assembly within an area which is approximately concentric with said annular casing; and a plurality of wiper members secured to the underside of said annular cover means, said wiper members being operative to space the cover means from the screen to enable said substance to move along the upper surface of the screen, and said wiper members being operative, during operation of the separator, to move with the cover means relative to the screen in such manner as to dislodge portions of the substance which may coat the upper surface of the screen.
 2. A wiper assembly as in claim 1 wherein the cover means is flexible.
 3. A wiper assembly as in claim 1 wherein an opening is provided in the center of the annular cover means, which opening is slightly larger than a feed pipe for providing the substance to be separated to the vibratory separator.
 4. A wiper assembly as in claim 1 wherein each wiper member is generally elongated and extends radially from the center of the cover means.
 5. A wiper assembly as in claim 4 wherein each wiper member comprises an elongated, flexible member mounted in a U-shaped channel which, in turn, is secured to the underside of the annuLar cover means.
 6. A wiper assembly as in claim 1 wherein each wiper member is arcuate in configuration and is pivotally secured intermediate its edge surfaces to the annular cover means.
 7. A wiper assembly as in claim 6 wherein each wiper member is made of a flexible rubber material.
 8. A wiper assembly as in claim 1 wherein the annular cover means comprises an annular flexible member of smaller diameter than said annular casing, and an annular reinforcing member of lesser diameter than said flexible member, which reinforcing member is secured to the lower portion of said flexible member.
 9. A vibratory separator having an annular casing comprising: a horizontal separator screen; a support screen parallel to and below said separator screen and have apertures greater than that of said separator screen; a plurality of anti-blinding rings having substantially flat upper and lower end surfaces disposed between said screen so as to be supported by said support screen; a wiper assembly means mounted on the upper surface of and and freely movable relative to, said separator screen and said wiper assembly comprising an annular cover means of smaller diameter than said annular casing, said cover means including an opening for allowing the substance to be separated to be passed to the region intermediate the cover means and the separator screen, said wiper assembly means further including a plurality of wipers secured to the under side of said annular cover means, said wipers being operative to space the cover means from the separator screen to enable such substance to move along the upper surface of the separator screen, and said wipers being operative during operation of the separator to move with the cover means relative to the separator screen in such manner as to dislodge portions of the substance which may clog the upper surface of said separator screen, and a feed pipe means for introducing said substance to be separated to said opening in said cover means, said feed pipe means extending to an elevation which is lower than the elevation of the top of said opening in said wiper assembly whereby the lower portion of said feed pipe limits the excursion of said wiper assembly within an area which is approximately concentric with said annular casing.
 10. A vibratory separator as in claim 9 wherein the cover means is made of flexible material.
 11. A vibratory separator as in claim 10 wherein the flexible cover means member is reinforced by a ring member of smaller diameter than said flexible cover means member.
 12. A vibratory separator as in claim 9 wherein said cover means includes a central opening, with the size of the central opening being slightly greater than the size of the feed pipe for the substance to be separated.
 13. A vibratory separator as in claim 9 wherein each wiper comprises an elongated member extending radially from the center of the annular cover means.
 14. A vibratory separator as in claim 13 wherein each wiper comprises an elongated U-shaped channel member into which is fixedly mounted an elongated rubber member which engages the upper surface of the separator screen.
 15. A vibratory separator as in claim 9 wherein each wiper comprises an arcuate member which is pivotally secured to the cover means at a point intermediate its edge surfaces.
 16. A vibratory separator as in claim 15 wherein each arcuate member is made of a flexible material.
 17. A wiper assembly for a vibratory separator including a generally horizontal separator screen mounted in an annular casing, said wiper assembly comprising: an annular, flexible cover means of smaller diameter than said annular casing, said cover means being disposed above the separator screen and freely movable relative thereto, said cover means including a central opening for receiving a feed pipe to enable substance to be separated to be passed to the region intermediate the cover means and the separator screen; said feed pipe means extending to an elevatIon which is lower than than the elevation of the top of said opening in said cover means whereby the lower portion of said feed pipe limits the excursion of said wiper assembly within an area which is approximately concentric with said annular casing; and a plurality of wipers secured to the underside of said annular cover means, said wipers being operative to sapce the cover means from the screen to enable said substances to move along the upper surface of the screen, said wipers being operative, during operation of the separator, to move with the cover means relative to the screen in such manner as to dislodge portions of the substance which may coat the upper surface of the separator screen.
 18. A wiper assembly as in claim 17 wherein each wiper comprises an elongated member extending along a radius of said annular cover means, each wiper comprising an elongated U-shaped channel secured to the cover means, and having mounted therein an elongated, flexible wiper member which is adapted to contact the upper surface of the separator screen.
 19. A wiper assembly as in claim 17 wherein each wiper comprises an arcuate member pivotally mounted to the annular cover means.
 20. A wiper assembly as in claim 17 wherein the cover means is partially slit along radial lines in such manner that the outer peripheral portions of the cover means engage the separator screen.
 21. A wiper assembly as in claim 17 wherein each wiper comprises a brush. 